There is a large variety of known automatic filling machines for flexible tubular packaging, such as mesh bags for packaging fruit and vegetable products, which generally comprise a pair of clips that hold the packaging to be filled through its upper aperture, in an open position, while the packaging is filled. Once the packaging has been filled, it is then closed, which is normally achieved by pushing together the clips holding the packaging, closing its upper part, then joining the two opposite closure portions of the edge of the packaging's upper aperture.
In order to ensure an optimum closure of the packaging, it is common to fold the lateral portions of the packaging between the closure portions that have been joined, so that the resulting folds are positioned, at least partially, between said joined portions, these lateral portions being folded similarly to an accordion.
A particular type of folding device that is applicable to the closure of this type of packaging comprises two folding blades disposed opposite each other in a direction perpendicular to a respective lateral portion of the packaging, attached to a respective axis of rotation that transmits thereto a reciprocating rotational movement around the axis. In each operational cycle, the folding blades rotate first in the direction towards the packaging to be closed, its ends pushing the respective lateral portion of the packaging and creating an inward fold, and subsequently rotating in the opposite direction, recovering their initial position in order to receive the next portion of packaging to be filled and closed.
The folding blades take the form of a flat plate and they are provided on their lateral edges with a tab in the form of a hook. This tab is adapted to hold and push the packaging during the folding operation by retaining at least one of the openings in the mesh of the opposite portion of packaging.
The use of the aforementioned folding blades tends to put a strain on the threads or tapes of the mesh of the packaging when the blades rotate and push the respective lateral portions inwards and the tabs pull on one of the openings in the mesh. This strain can cause the mesh of the packaging to be damaged or even broken during the subsequent handling of the filled packaging.
Furthermore, in the use of devices for the closure of packaging by sticking together said opposite portions that include the formation of lateral folds, it is normal for small sections of the strands that form the threads or tapes of the packaging to protrude from the opposite lateral portions that are stuck together, causing a flawed outer appearance or a poor presentation of the packaging filled with the product.